1. Field of the Invention
The present invention relates to a method and a device for recognizing handwritten letters which is capable of readily recognizing a handwritten letter that is input by writing through a coordinate inputting device, without regard to the order of strokes of the letter.
2. Description of the Prior Art
In the recent years there have been proposed various kinds of handwritten letter recognition devices for recognizing handwritten letters. The letters are input by writing on a coordinate inputting device such as tablet device by utilizing information on the strokes. Data on the letters is input that represent the handwritten letters into a computer or the like by encoding the data. In one example of the prior art recognition device, a letter pattern, which is input by writing on a letter inputting section consisting of a coordinate inputting device, is fed to a pre-processing section, and after applying to it such preliminary processings as removal of input noise and normalization of the letter size, stroke information on the input letter pattern is extracted at a characteristics extraction section. Then, the information on the stroke characteristic which represents the input letter pattern is matched in a matching section with stroke information for each standard pattern in the recognition object categories that have been registered in advance in a standard pattern dictionary, to find the degree of similarity, distance, and others between the input letter pattern and each of the standard patterns. The information on the degree of similarity and the distance thus found for each one of the standard patterns is evaluated at the discrimination section to obtain the result of recognition for the input letter pattern as a recognition object category.
Now, the input letter pattern discussed above is given as a sequence of strokes that are written on the tablet surface, and the order of strokes may be different from the regular order of strokes. Because of this, it was necessary to carry out a very large collating computation if the input strokes were to be collated with all of the standard strokes of the standard patterns. therefore, in the past a correspondence has been established on the table between the strokes in the dictionary and the strokes that are input by writing, and the collating was carried out between the strokes that are in such a correspondence relationship. However, in the case of a large number of strokes in the input pattern, finding a correspondence relationship itself between the strokes becomes difficult, and hence there used to be a problem that the efficiency of the recognition processing was unsatisfactory.